Selena Gomez reportedly lost her cool while performing last Friday night in Los Angeles.
Dressed in a red bodysuit and a black wig, the 21-year-old singer finished singing one of her songs and then dropped the f-bomb.
"She for sure said, 'What the f---,'" a concertgoer told EOnLine.com. "You could hear it crystal clear."
The concertgoer also said Gomez appeared to be lip synching while using a backup track: "She was messing around with her ear piece from the first song so you knew something wasn't right."
"Sorry, the sound is not working!" Gomez told the crowd filled with mostly children. "Are you guys having a good night? There's a lot cooler people that are gonna come out tonight. Is it okay if I perform two more songs and you guys can get to it?"
Gomez kept talking to the crowd, apparently buying time for the tech problems to be fixed.
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"I have to thank you guys so much for allowing me to be able to perform the music that I love," added Gomez. "And I have to say that before you guys go on to the people that you care about, I really appreciate you supporting everything that I do. So this next song is the first song I had hit number one, and it's called 'Come & Get It.'"
However, she didn't do a second song as promised and walked off the stage, another concertgoer told Us Weekly.
"She was pissed doing the next song and she said two more songs," recalled the concertgoer. "[She] didn't do the last one."